A hard drive may be tested under various conditions for determining whether the performance of the hard drive is consistent over the various conditions. For example, the bit error rate of the hard drive may be determined at a first temperature and compared to the bit error rate of the hard drive determined at a second temperature. The performance of the hard drive may be considered inconsistent if the difference between the two bit error rates is significant. Thus, the hard drive may be designated as a failure. To ensure reliability, a limit for the maximum allowable difference in bit error rates may be set such that even a small difference between the two bit error rates that exceeds the limit may indicate that the hard drive is a failure. On the other hand, setting the limit in this manner may also result in unnecessarily designating hard drives that may otherwise be suitable for use as failures. Therefore, it would be advantageous to test hard drives reliably without unnecessarily failing too many hard drives that may otherwise be suitable for use.